A chain oil-well pumping unit as disclosed in CN Patent Application No. 86102979 includes five subunits:
(1) Driving system including motor, pulley, speed reducer and shaft coupling; PA1 (2) Reversing system including drive chain wheel, upper chain wheel, locus chain, main shaft pin, special chain element, slide block and reciprocating rack. PA1 (3) Counterweight system including counterweight chain, counterweight chain wheel, counterweight trunk piston, counterweight cylinder, gas energy accumulator, oil pump and air compressor. PA1 (4) Suspension system including cable suspension, steel cable and pulleys. PA1 (5) Framework including base, speed reducer base and framework body.
The Driving Principle: The motor drives the drive chain wheel through the belt and speed reducer. The locus chain moves vertically between the drive chain wheel and the upper chain wheel. The special chain element on the locus chain drives the reciprocating rack through the main shaft pin and the slide block. The rack moves up, down and reciprocally along the path as the locus chain moves annularly. The steel cable is linked at the central position with the top end of the reciprocating rack and linked with the cable suspension through the pulley. The cable suspension is linked with the polish rod so that the vertically reciprocating motion of the rack causes the up-down stroke of the rod. The counterweight chain is linked at the central position of the lower end of the reciprocating rack and linked with the pneumatic counterweight system to realize the balance of the oil-well pump unit. The unit has strong points such as long stroke, lower stroke times, high efficiency, large loading and electrical efficiency. However, its structure is complicated, there is a tilting moment vertical to the chain moving plane in the reciprocating rack and the pneumatic counterweight system malfunctions easily, the eccentricity of the shaft coupling can not be regulated, shock is serious in reversing, the load center is off the frame, stability is lower, and maintenance is difficult, etc. Therefore, its development has been limited.